The European elm scale in the west

Historic, archived document

Do not assume content reflects current
scientific knowledge, policies, or practices.

Washington, D. C. July 10, 1924

THE EUROPEAN ELM SCALE IN THE WEST.’

By Frank B. HeErsert, Scientific Assistant, Forest Insect Investigations,
Bureau of Entomology.

CONTENTS

Page. | Page.
RMAEMAT HE 1 Life history and habits__________ 9
OLD UU ME G2 Se el 1 Seasonal history —_ Ps - ae P 11
eus¢pry-=- - 3s ee eee 2 | Natural enemies__________ Vee 12
Synony my es Fe Control expermments 2 a SE 13
Distribution and spread at ee _ 5 | Recommendations for control ______ 15
i a pitoios ppetan FT oy nary 8 = eon ae 17
Food plants_______ 2G Falher ee ie). akteree Cited 3 oe ae Fee er 18
_ ISSR aa 6 |

INTRODUCTION.

The European elm scale, Gossyparia spuria (Modeer), has long
been known in Europe and the Eastern United States as a serious
enemy of the elm. It was first discovered in the West in 1893, when
E. M. Ehrhorn found it infesting elms on the Stanford University
campus, Palo Alto, Calif. Prompt measures of eradication were
attempted, but were not entirely successful. Since that time it has
spread from this or other sources until it is now quite widely dis-

tributed throughout the West. It is becoming of considerable impor-

tance as a shade-tree pest owing to its distribution and to its par-
ticularly aggressive habits in newly infested localities.

IMPORTANCE.

The elm is probably the most popular shade tree in America. It
attains good size, produces a luxurious amount of green foliage, and
is planted throughout the United States and elsew here in dooryards,
along streets, and in parks for shade and ornament. In the East

t Acknowledgments are due to Dr. A. D. Hopkins, Ferest Entomologist: H. FE. Burke,
Specialist in Forest Entomology : Harold Morrison, Coccidologist; and others, for helpful
suggestions and observations; to W. S. Fisher, Specialist in Forest Coleoptera, for identi-
fication of the coccinellid predators : to S. B. Doten, Director and Entomologist of the
Nevada Agricultural Experiment Station, and to Frank N. Wallace, State Entomolcgist of
Indiana. for the use of a number of illustrations used in this publication,

? Resigned June 30, 1920.

69577°—24——__1

2 BULLETIN 1223, U. 8. DEPARTMENT OF AGRICULTURE.

the native elm also produces wood which is particularly valuable it
the making of vehicles, baskets, crating, ete. |

The European elm scale infests all species of elm, having become
such a very disagreeable and harmful pest that in many eastern
localities these trees are no longer recommended for planting. In
the West the scale insect is not so widely distributed, nor are many
of its eastern associates present, so that in spite of the elm scale the
tree 1s still recognized as one of the best for shade.

Fortunately, the scale in America infests only elms and is not ¢
pest on fruit or other shade trees, as are many of the aggressiv
scale insects.

HISTORY.

This insect was first noted in the United States in 1884, when
Charles Fremd found it infesting elm trees in his nursery at Rye,
Westchester County, N. Y. It had undoubtedly been imported
from Europe, where it has been known for nearly 200 years. It
was next reported by Professor Comstock from New York City,
where he had found it rather abundant in the winter of 1886-7. A
few months later John G. Jack sent specimens to the United States”
Bureau of Entomology from slippery elm growing at Cambridge,
Mass. In 1888 it was found at Washington, iD: ee infesting elms |
on the grounds of the Department of Agriculture and also in two
localities on the streets of the city.

Up to this time it had not been positively identified, but the next
year Dr. L. O. Howard made a thorough study of the insect and _
identified it as the European elm scale (10).

A few years later this scale insect was found to have invaded the-
western part of the United States. In 1894, Alexander Craw (2),
of the California State Board of Horticulture, reported that during
the previous season E. M. Ehrhorn had noted the European elm
scale upon elms at Stanford University, California. The next year.
Mr. Hillman, entomologist of Nevada, reported it from Reno, Nev.,
and in 1906 A. lL. Melander (6), entomologist of Washington, —
stated that it had been in Spokane, Wash., for several years.

From time to time it has been reported from one State or another
until it is now known to occur in 27 States besides the District cf
Columbia.

SYNONYMY.

As abel as 1788 this scale was known in n Europe, at which time —
Reaumur (8) figured the female in all its stages and gave its
natural history, but failed to give it a name except that of “pro-
egallinsecte ” of the elm.

The first name given to it was Coccus ulmi by Linnaeus (74, p. 265)
in 1761. In 1875, Signoret (19, p. 27) removed this insect from the
genus Coccus and erected a new genus, Gossyparia, with w/mi as
the type. The specific name wlme was retained until recently, when
it was discovered that it rightfully belonged to another insect named
Coccus ulmi Linnaeus (1 3, p. 455) in 1758, since removed to the
genus Lepidosaphes. Consequently the next ‘specific name used for
the Huo pena elm seale, spwr?us, anvlied to it in 1778 by Modeer

q

3 iNumbers in a ee (italic) refer to Literature cited, p. 18.

THE EUROPEAN ELM SCALE IN THE WEST. 3

(17), was adopted, so that now the proper name is considered by
most entomologists to be Gossyparia spuria (Modeer).
The latest change has been by the European coccidologist Lind-
inger (12, p. 331). who put this species into Eriococcus, where the
writer feeada we that it rightfully belongs. No move has been made
toward accepting this name in the United States so far, however,
so that the writer does not feel inclined to use it in this paper.

The two genera, Gossyparia and Eriococcus, are separable only
from the fact that the adult female of the former secrets a semi-
cocoon, while the latter entirely covers itself with a cottony cocoon.
This means that Gossyparia spuria lacks wax- -secreting glands on
the dorsum, which can har dly be considered a generic character. If
the name Lricoccus spurius is accepted, then the genus Gossyparia
will become a synonym of Eriococcus, as spuria is the type of that
genus.

From time to time this insect has been referred to under the fol-
lowing names: Coccus ulmi, C. spurius, C. laniger, C. gramuntii,
Chermes ulmi, Nidularia lanigera, N. qramuntii, Gossyparia ulmi,
G. gramuntii, G. spuria, and finally Eriococcus spurius.

DISTRIBUTION AND SPREAD.
DISTRIBUTION.

This common pest is widely distributed, not only in North
America but also in Europe, where it reaches from Spain to Tur-
key and as far north as Norway. Kuwana (//) has also reported it
from the province of Shinano, Japan. The writer has seen speci-
mens from there collected by Mr. Kuwana, however, which undoubt-
edly are not Gossyparia spuria, but are some rather closely related
species. The writer is informed that Mr. Kuwana is now of the same
opinion. Instead of being encircled with fringe of wax, the body of
the mature female is entirely covered with it—a character which
should place this species in the genus Eriococcus.

In America the scale is found both in C anada, where it has been
reported from the provinces of Ontario and Quebec, and in the
United States, where it occurs in 27 States and the District of
Columbia. It is still spreading, for occasionally a new State is
added to the list. The scale is known to occur in the following East-
ern, Central, and Southern States: Maine, New Hamshire, Vermont,
Massachusetts, Rhode Island, Connecticut, New York, New Jersey,
Pennsylvania, Maryland, District of Columbia, Virginia, West Vir-
ginia, Ohio, Michigan, Wisconsin, Indiana, ‘Tllinois, Iowa, Mis-
sourl, Alabama and Louisiana.

In the west the scale occurs in the following States: Colorado,
Utah, Nevada, Idaho, Washington, and California. (Fig. 1.) Its
distribution in these States is more or less limited) In Colorado,
C. P. Gillette, State entomologist, reports that it has been doing
damage for some time in the city of Denver. George M. List (/5),
his chief deputy, has since reported it from Golden and from near

Fruita, Mesa County. W. W. Henderson, entomologist of the Utah
| Agricultural Exper iment Station, states that to his personal knowl-
edge it exists in isolated places about 100 miles north and south

‘¢
2

4 BULLETIN 1223, U. S. DEPARTMENT OF AGRICULTURE.

of Salt Lake City and in the region between these two extremes,
where it occasionally does severe damage. In Nevada it is confined
to a limited area in the west-central part of the State, extending
from Carson City to Reno, according to S. B. Doten (3, 5), director
of the Nevada Agricultural Experiment Station, and from the
writer’s personal observations. A. L. Melander (/6), entomologist
of the Washington Agricultural Experiment Station, reports that
he has not found it anywhere in the State of Washington, except
at Spokane, where it has been for 15 years or more. The files of
the Bureau of Entomology also contain records of this insect oc-
curring at Coeur d’ Alene and Boise, Idaho.

In California, the insect is somewhat more widespread, occuring
in a number of localities in the northern and central portions of
the State. It has been found in or near the following towns: Ukiah,
San Rafael, Colusa,
Woodland, Davis,
Sacramento, Stock-
ton, Modesto, Oak-
dale, Woodside,
Redwood City, Palo
Alto, Stanford Uni-
versity, Mayfield,
Mountain View, Los
Altos, Santa Clara,
College Park, San
Jose, Milpitas, Eden-
vale, Los Gatos, and
Saratoga.

Additional locali-
ties in the United
States and Canada
have been recorded
by Albert Hart-
zell (8).

SPREAD.

The elm scale was
Ite. 1.—Known distribution of European elm scale in the

West. in all probability

brought to America

from Europe on young elm trees. The shipment of elm stock from

infested nurseries to various parts of the United States has also been
the cause of its being scattered over such a wide territory.

In these infested localities the scale has spread from tree to tree
by several agencies. Birds, such as English sparrows, which are
to be found in large numbers in the shade trees of almost any town,
probably carry the young crawling scales for considerable distances
on their feet. During the fall infested leaves drop to the ground
and are blown for some distance by the wind. A certain percentage
of these larve happen to find themselves at the base of an elm tree
and crawl up to start a new infestation. The European elm scale
has been seen spreading in this manner by both Professor Doten
and the writer, The Argentine (/ridomyrmex humilis Mayr) and

THE EUROPEAN ELM SCALE IN THE WEST. Bs)

other ants are known to transport scale insects from one tree to
another in order to increase their food supply, and this method of
transportation probably applies to this species as well as to others,
since it is usually attended by a great many ants. Elms are nearly
always planted so close that some of their branches interlace, en-
abling the larve to crawl at will from one tree to another. Thus
it is not long before
the European elm scale
has thoroughly — estab-
lished itself upon most
of the elms in a locality.

INJURY.

Thousands of these
scale insects sucking
the plant juices from
the leaves, twigs, and
branches (figs. 2, 3)
cause considerable in-
jury toelm trees. Their
effect upon the elm is
shown by yellowing and
premature dropping of
the leaves, stunting of
growth, and dying twigs,
branches, and entire
trees. Their injury is
most apparent on young
trees, which occasionally
they kill. Mature trees
are seldom killed.

A less serious trouble
is the production of a
considerable amount of
honeydew. which covers
the leaves, twigs, and
branches, making them
black and sticky. It also
drops on the street and
sidewalk, making the
pavement slippery and ; : 7
dangerous to passing ve- "%* 2—Adwlt females of European elm scale on elm
hicles, besides having an 3
unpleasant appearance and odor. Many disagreeable insects are
attracted by the honeydew.

In some sections the American elm is reported as the favorite
host of the European elm scale, while in other localities the English,
Camperdown, or slippery elm is reported to be the favorite. The
American and Camperdown elms seem to be preferred by it in Cali-
fornia. Probably the degree of infestation depends upon the con-
dition of the tree more than upon any other factor.

6 BULLETIN 1223, U. S. DEPARTMENT OF AGRICULTURE,

Trees which have been attacked for a number of years by this
insect, 1f they do not die, finally seem to develop a certain amount
of resistance to its injury. The history of this scale insect through-
out North America has been much the same. It causes much con-—
cern to the owners of shade trees for a number of years after mak-
ing its first appearance, and then seems slowly to lose its grip upon
the trees until 1t causes a much smaller amount of damage. This—
is especially true in sections of the Eastern States and Canada,
where less attention than formerly is now paid to this once dreaded
insect.

FOOD PLANTS.

The recorded food plants of the European elm scale in the United.
States are English elm (Ulmus campestris), Scotch or Wych elm —
(U. scabra), European species, and white or American elm
(U. americana), cork elm (U. racemosa), and slippery elm (U.
fulva), American species, and their varieties. Probably all species
of elms are subject to attack by this insect, although some have not —
yet been recorded as host to it.* }

Tn 1895 Lintner, then State entomologist of New York, collected
immature specimens of a scale insect on willow at Loudonville,
N. Y., which were determined at that time as the Kuropean elm
scale. This determination has since been corrected and those speci-
mens have now been identified as a species of Eriococcus.

Signoret (79, p. 21), a French entomologist, has stated that he
collected Gossyparia spuria on alder in France. Lindinger (72, p.
54, G4, 122, 159, 338), also a European entomologist, gives the fol-
lowing hosts in addition to elm: Acer sp., Alnus sp. (very prob-
bly Signoret’s record), Corylus avellana, Frarinus excelsior, and
Viscum album, all European records. From the fact that the Kuro-
pean elm scale has not been found on any of these hosts in America,
the writer is inclined to believe that some related species has been
confused with it. At any rate there are no records of the European
elm scale occurring on anything except elms in America. The
writer has seen both alders and willows growing with their branches
interlaced with those of infested elms, yet not a scale could be
found on either of them. One specimen of Zelkova acuminata,
which belongs to the elm family (Ulmaceae), has been seen growing
near a large number of infested elms, but no infestation was
apparent upon it.

DESCRIPTIONS.
EGG “(PI I, “A);
Oval in outline, twice as long as wide, 0.36 by 0.19 millimeter. Color bright

yellow; surface smooth and shiny. Eyes of larva visible as two black spots
through the egg membrane.

4 Aside from the European elm scale the principal insect pests of the elm in the West
are the carpenter worm, Prionorystus robiniae Peck, which bores into the trunks and
main limbs, often killing large branches and occasionally whole trees; an aphid, Myzo-
callis ulmifolii Monell, and a leafhopper, Empoa ulmi L., both of which suck the plant
juice from the elm leaves and produce an abundance of honeydew. They are sometimes
worse than the elm scale in this respect. ;

The elm leaf-beetle, Galerucella luteola Miill., is probably the worst enemy of the elm
in the East. where it defoliates a great number of trees every year. It has also been
introduced into the West, having been reported several years ago from Portland, Oreg.
This has not yet become a serious pest in the West, but may in the near future.

THE EUROPEAN ELM SCALE IN THE WEST. -

LARV.
Figst Srace (Pu. I, B).

Color bright yellow soon after hatching. Length 0.45 millimeter; width
0.19 millimeter. Of an elongate oval form, rounded anteriorly and tapering
posteriorly to a pair of pointed processes, each bearing one long and several
short sete. Anal ring, occurring between these processes or lobes, with six
setz or hairs. Legs rather stout, with short tibize. Usual two pairs of thoracic
spiracles present. A single row of blunt spines on the lateral margin of larva
and a double row extending down the back, some reduced to rudiments. Also

winter on corky elm
(Doten. )

Fic. 3.—Females of the European elm scale: 1, Dead females in
(natural size) ; 2, living females in summer (enlarged about 4 diameters).

six extra spines on head and a number of very small spines on dorsum. An-
tenn (Pl. III, A) rather stout and 6-segmented, sixth segment longest, fourth
and fifth subequal and shortest, each segment bearing several hairs.

SEconD Stace (Pt. I, C).

Full-grown second-stage larva reddish brown in color. (In life of a gray
appearance, due to the protruding wax.) 3ody oval in outline, rounded ante-
riorly and rather pointed posteriorly, about 1.1 millimeters long and 0.6 milli
meter wide. Eyes situated near margin of body behind antennz. Legs rather
long and slender. Two pairs of thoracic spiracles present. Anal ring com-
pound, bearing six sete and situated between two prominent pointed anal
lobes, each bearing a long slender spine on its tip, also several shorter spines
on lobes. Entire dorsum covered with stout blunt spines and arranged more
or less in two rows on each abdominal segment. Few small spines on venter.

8 BULLETIN 1223, U. 8S. DEPARTMENT OF AGRICULTURE.

In this stage one is able to distinguish the difference in sexes by th
number of antennal segments. Antenne of male larva 7-segmented, first seg-
ment broadest and seventh longest (Pl. III, B). Female larva with 6-segmen
antenne, quite similar to those of male, except that third and fourth segments
have been replaced by one long segment, practically equalling the other two
CesT, C).

Both sexes have pores of the quinquelocular type (Pl. III, #) on the venter,
but only the male larva has large circular pores on the dorsum and margin
of the venter. These circular pores communicate with internal cylindrical
ducts, which bear cup-shaped depressions on their inner ends (Pi. III, @),
and are presumably the ones used in secreting the wax to form the pupal
cocoon.

ADULT OR THIRD-STAGE FEMALE (PL. I, D, FE).

Female dull red-brown or green-brown after molting, elliptical in outline,
later becoming oval and at the same time forming a waxy fringe about the
margin of the body. Upon becoming engorged with eggs the adult female
attains a length of 2.1 millimeters and a width of 1.8 millimeters. Antenne
(Pl. III, D) distinctly 7-segmented, third and fourth segments longest, fifth
and sixth shortest. Previous writers have not always agreed upon the number
of antennal segmen.s possessed by the adult female. In some species the
number is not constant; however, all western specimens examined possessed ~
7-segmented antenne.

Usual coccid mouth parts and two pairs of thoracic spiracles present. Legs
(Pl. III, J) rather long and slender. Anal ring compound, bearing eight
sete, and situated between two prominent lobes (Pl. III, H), each bearing
three dorsal spines and one termina! and two ventral sete, also a number of
nodules which are particularly prominent and abundant on the inner surface.
Entire dorsum covered with stout blunt spines, arranged as in preceding stage.
Small slender spines and pores of quinquelocular type (PI. III, #) on venter.
Large circular pores (Pl. III, G) occur on dorsum and margin of body,
being more plentiful on latter. These communicate with internal -cylin-
Grical ducts which bear cup-shaped depressions on their inner ends. There
are also a few very smail circular pores on the margin of the body communi-
eating with small, slender, internal tubular ducts.

MALE PREPUPA (PL. II, A).

The second-stage male larva after forming a cocoon molts to a prepupa,
which is the first dormant stage of the male. Color brownish red. Length
1 millimeter, and width about 0.5 millimeter. Oval in outline with head
somewhat pointed. Apex of abdomen 3-lobed, a slender seta occurring on each
outer lobe. Antennze and-legs not now long and slender, but short, thick, and
immovable. Antenns# indistinctly 10-segmented. Very short wing pads present.
No eyes visible and mouthparts lacking. Segmentation of body indistinct.

MALE PUPA (PL. II, B).

The second dormant stage of the male.is also passed in the cocoon. ‘This is
a separate stage from the prepupa, a -molt- having taken place in between.
Brownish red in color, oval in outline, slightly longer (1.1 millimeter), and
more slender than prepupa. Top of head -more rounded and tip of abdo-
men more distinctly three-lobed, central lobe larger and more pointed.
Antenne large and heavy, distinctly 10-segmented, reaching to base of wing
pads. Wing pads larger, reaching to middle femora or beyond. Legs more
distinctly segmented, longer and more slender, anterior pair folded over
“ face.’ Body more distinctly segmented; mouth parts lacking,

ADULT MALE.

Reddish brown in color and longer and more slender than pupa; 1.3 milli-
meters long and 0.4 millimeter wide. Head rounded, truncate between an-
tennze. Eyes black, with usual dorsal pair present and one ventral pair
replacing mouth parts. Antenne rather long and hairy, 10-segmented. Legs
long and slender, tibia longer than femur. Caudal end 3-lobed, middle lobe
large and pointed, bearing the genital organs; all -three lobes bearing a
number of set#. Two large setz# on each outer lobe surrounded with a number

Bul. 1223, U. S. Dept. of Agriculture.

ZEPPLBIYNN Wat
ZCOAAMPAANRIS

EUROPEAN ELM SCALE.

iA gees B; Dorsal view of first-sta
arva. (Second-stage male larva is i

D, Dorsal view of newly molted or virgin female.

e larva. C, V

entical except f

E

0

entral view of second

r antenne, which

-stage female
are 7-segmented.)

, Ventral view of mature female.

PLATE II.

Bul. 1223, U. S. Dept. of Agriculture,

TG is Ree COTS Et

EUROPEAN ELM SCALE.
A, Male prepupa. B, Male pupa. C, Wingless male adult. D, Winged male adult.

oa PE

Bul. 1223, U. S. Dept. of Agriculture. PLATE III.

|

| /

|

'

|

|

| A
E

))
f)

&

EUROPEAN ELM SCALE.

A, Antenna of first-stage larva. B, Antenna of second-stage male larva. C,

Antenna of
second-stage female larva. D, Antenna of adult female. £, Quinquelocular type of pore.

F, Trilocular type of pore. G, Circular pore and cross-section of internal communicating
duct. H, Ventral view of tip of abdomen of adult female. J, Leg ol adult female.

PLATE IV.

3, U. S. Dept. of Agriculture.

22

1

Bul.

EUROPEAN ELM SCALE

in elm (X 10).
(Doten.)

k
B, Larve and male cocoons in early spring (X 16).

aled in crac

y conce

artl

p

in winter

Larvee

A,

PLATE V.

ure.

ve
L

Bul. 1223, U. S. Dept. of Agricul

CALE.

EUROPEAN ELM S

1 under

midrib or
cocoons on

)

alons

A, Larve in late summer

Male

16).

en.)

surface of elm leaf (

elm bark (xX 10).

(Dot

PLATE VI.

SUTyS ySvO ‘MOOD0_ ‘¢

‘oreur pesurmM “7

On i

(‘uej0q) ‘wdnd pure evAiez jo
‘SOTBUT SSOTSUTAA ‘¢ pues “SJUSUTeTY [vue pue SssuUIM Sutpnayoid YAM W00d0| ‘7

“AIVOS W14y NVadOdYeNS

THE EUROPEAN ELM SCALE IN THE WEST. 9

of trilocular pores (Pl. III, /'). These are presumably what produce the wax -
filaments on some males.
There are two forms of the male, winged and wingless. The winged form
(Pl. Il, D) has full-sized wings folded over the dorsum when not in use, while
the wingless form (PI. II, C) has only short wing pads. The body of the wing-
less form is occasionally broader than that of the winged. There are, moreover,
~ all grades between these two extremes, having all sizes of malformed wings.
Two wax filaments, borne on the anal lobes, extend posteriorly and equal the
length of the body in perfect males. These also vary in length, however, and
_ may be present or entirely lacking on either the winged or wingless forms.

LIFE HISTORY AND HABITS.

In the spring after mating the female scales are found to con-
tain a few eggs. By the time “they have completed their semicocoons,
_ however, they are well filled with eggs and have increased consid-
erably in size.

OVIPOSITION.

The eggs remain in the body of the adult female until the embryos
are about to hatch. As each embryo becomes fully developed the
egg is expelled ventrally from near the tip of the abdomen. They
are thus laid in a sort of pocket, being protected by the body of the
mother and the surrounding fringe of wax.

Each female is capable of laying a large number of eggs. Adults ex-
— amined on July 5, 1919, after having laid for some time, contained from
_ 97 to 138 eggs. Professor Doten, of Nevada, reports having counted
_ 60 to nearly 300 dead larvee, which had been unable to escape from
under different females. A drawing of the ovaries of an adult
female by R. E. Snodgrass (20, fig. 19), would indicate a still larger
number. He figures over 200 on one branch of the oviduct making
a total of approximately 425 eggs from one female. This would
indicate that the rate of increase is quite large, yet not as great as
that of many other scale insects.

The eggs are laid slowly, covering a considerable period of time,
and only during the warm part of the day. One female observed
laid 16 eggs in 54 hours, or 1 about every 20 minutes. The larve
hatch from these eggs ¢ honk 40 minutes later and are ready to crawl
away in another half hour.

It has several times been reported that the adult females give
birth to living young. These misstatements are probably due to the
- fact that the eggs hatched very soon after deposition and were not
seen by these observers.

LARV.

Newly hatched larve are active and soon seek a place for attach-
ment. Some attach themselves to twigs and branches, while a large
majority of them migrate to the leave es, where they settle on both
the upper and lower surfaces along the midribs, the aa ence of
the leaf-veins affording them some protection. (Pl. V, 4.) They
remain in these positions until fall. By this time ine are second-
stage larve, having undergone their first molt about six weeks after

hatching. 7

10 BULLETIN 1223, U. S. DEPARTMENT OF AGRICULTURE.

In the autumn, when the leaves begin to fade and fall, these larv
move to more permanent places, locating in the crevices of the bark
on the twigs and branches (Pl. [V, A) and clustering about the win- |
ter buds, where they spend the winter. Some of the larve fail to |
move from the leaves before these fall from the trees, and are carried
considerable distances by the wind. Some of these die from starva-
tion, while others crawl up the trunks of near-by trees to new feeding
grounds.

The first-stage larve excrete very httle wax, but the second-stage
larvee are weil covered with sugary-appearing particles of it. This
protects them in the winter from frost and rain and incidentally
makes them immune to any mild form of spray material.

The larvee remain in the second stage for from six to seven months,
or from late summer to late winter or early spring. The male larve
are the first to leave their winter quarters. In fact, some of them
do not wait for winter to end, for on the first mild days in late
January they begin to form their cocoons in which to pupate. They
seem to be particularly fond of making their cocoons (Pl. IV, 2) on
dead twigs or branches, in the bark crevices, or near the crotches of
living limbs. Their cocoons may even be found massed together in
large white patches (Pl. V, 4) on smooth exposed parts of the trunk
or branches.

ACTIVITIES OF THE MALE.

The cocoon is made of waxy threads, secreted from the pores on
the body of the larva. These are woven and twisted about until a
definite covering has been formed. After completing the cocoon,
which requires several days, the larva changes to a prepupa, which is
the first dormant stage in the transformation from larva to adult.
A definite molt takes place at this time, the cast skin being pushed
out through a shit in the rear end of the cocoon.

A week or so later another molt occurs, this time to a true pupa,
the second cast skin being pushed back out of the cocoon. (PI. VI,
5.) This stage occupies from one to two weeks, whereupon the pupa
changes either to a winged (Pl. VI, 4) or a wingless (PI. VI, 2, 2)
adult male. All the first pupe to transform become wingless males,
while all the last become winged males. During part of the inter-
vening time both winged and wingless adults can be found, together
with different forms between these two extremes. For instance, -
some males will have partly formed to nearly fully formed wings,
while the wax anal filaments may vary from partly formed to full
length or even be entirely lacking on either extreme. ‘Temperature
and humidity probably cause these variations. E. P. Felt (7), of
New York, reports a definite period occurring between the appear-
ance of the two forms of the adult male in the State. There is no
such period in the West.

The wax filaments may be seen protruding from the cocoons for
a day or so before the males emerge (Pl. VI, 7). which they accom-
plish by backing out. They live only a few days, dying soon after
they mate,

THE EUROPEAN ELM SCALE IN THE WEST. igt

ACTIVITIES OF THE FEMALE.

The hibernating female larve begin their activities a little later
| than the male larve. In fact, most of them show no sions of
activity until March, when they begin molting for the last time
m(Pl. IV, 2B). The white cast skins appear quite conspicuous on the
bark. The newly molted or virgin females are smooth and of a
-dull brown or greenish-brown color. After mating they move
about and settle cea for the last time, most of ‘hen selecting the
lower side of the larger limbs and branches. They soon take on a
3 grayer appearance and begin to form waxy fringes of cotton or
_ semicocoons about the margins of their bodies. By the middle of
© May they have about completed their semicocoons and are full.
grown, ready to begin oviposition. Egg laying lasts for several
~ months, or until about the middle of ‘August. During this time
_ the females have ‘slowly shriveled and die upon completing ovi-
position.

Soon after molting to the third stage thé females begin excret-
_ ing honeydew, and do not stop until egg laying is completed. This
_ drops onto the foliage and the ground beneath, making the trees
and ground very sticky. A black smut fungus grows in this sticky
material, giving the foliage a black appearance which can be seen
for erat distances.

SEASONAL HISTORY.

There is orly one generation a year of the European elm scale.
The second- stage male and female larve are the forms hibernating.
Late in January in the milder climates a few of the male larve
start forming cocoons in which to pupate. These become more
abundant during February and March. Adult males begin emerging
from their cocoons in February, becoming more abundant in March
and April. A few of the last to transform emerge in May.

The hibernating female larve molt for the last time in March
and April, whereupon they move to a proper place for the summer
and mate. They soon begin to increase considerably in size, at
the same time forming waxy semicocoons about their bodies. Egg
laying starts the last of May or the first of June and continues
through June, July, and part of August. Having completed ovi-
position the females shrivel and die.

The eggs hatch in less than an hour after being deposited and the
tiny yellow larve crawl about, some setthng on the twigs and
branches, but most of them settling along the midribs of the leaves.
About the middle of July the first of these larve molt for the first
time, becoming reddish brown and later gray from the sugary
particles of wax which are secreted over the back. The last of the
yellow larve> molt early in September. ‘These second-stage brown
or gray larve are the overwintering forms, and are found mostly
clustered about the winter buds and in the rough areas of the twigs
and branches.

A definite relationship has been observed between the activity of
- the European elm scale and its host. As the events in the life cycle

ata Peed ee ra ~
whi eo Werte ont ee ee eee

ee eo clas

Pee Pe OL a SE

12 BULLETIN 1223, U. S. DEPARTMENT OF AGRICULTURE.

of the elm are more evident than those of the scale insect, it is well
to indicate this relationship, especially since the time of application
of control measures often depends upon both. The tree and the
insect awaken from hibernation at the same time. The females
undergo their last molt while the fruit is forming on the tree. Most
of them have attained a large size and are secreting their semi-
cocoons when the fruit begins to fall from the tree. The semi-
cocoons are completed by the time most of the leaves are full grown,
and egg laying starts two or three weeks later. The second- -stage —
larve migrate from the leaves back to the twigs and branches when —
the tree sap becomes sluggish and the leaves begin to yellow and fall.

NATURAL ENEMIES.

The insect enemies of the European elm scale are very scarce and
play but a small part in its control. The first and only record of
the rearing of a parasite from this scale in the United States was
in 1898 by Rh. A. Cooley (7), who reared half a dozen specimens at _
Concord, Mass. These have never been described, but remain under
the manuscript name of Coccophagus gossypariae Howard. The
writer endeavored a number of times to obtain parasites from west-
ern material, but was unsuccessful. Either there are none in the
West or they are so scarce that they do not figure in the control of
this scale insect.

The predatory enemies of the European elm scale are somewhat
more numerous, but even they can not be considered as important
agencies in its control. The twice-stabbed lady-beetle, CAclocorus
bivulnerus Mulsant, is the most common enemy of the European
elm scale. Essig (6, p. 119-120) mentions that Dr. A. J. Cook
reported this beetle as preying upon the scale insect at San Rafael,
Calif. The writer also has observed beetles of this species feeding
upon the body contents of adult females.

Both larve and beetles of the black lady-beetle, Rhizobius ven-
tralis Erichson, ted upon this scale insect when in captivity. and in
all probability feed upon it when free, as it is usually found abundant
upon scale-infested trees. The common black-spotted red lady-
beetle, Hippodamia convergens Guérin, and its variety, ambigua
LeConte, have been found rather plentiful upon infested trees and
probably prey upon this scale insect, yet none have been observed
actually feeding upon it.

The green lacewing Chrysopa californica Coquillett has also been
reared upon the European elm scale and is found to some extent upon
infested elms. No other insect enemies of this pest have been
observed.

:

THE EUROPEAN ELM SCALE IN THE WEST. ~-- -13

CONTROL EXPERIMENTS.

. TABLE 1.—Haperiments performed upon the European elm seale.

Date. Spray material. Dilution. Trees. ae Remarks.
Per
cent.
pre 19USc) Watebon ci. 225 an. we os 100 to 160 pounds 191 85 | Used fire engine® and
pressure. hose, large trees.
Apr. 191918 |}. - GOS). -se ee hea: 50 pounds pressure. 2 95 | Used garden hose and
nozzle, small trees.
Wepie 20,1918.) 2... - DOP eat oe ae hs se GOesssscise5.: 1 80 | Used garden hose, ex-
tension rod, and 12-
foot platform, medi-

um-sized tree.
May 14,1919 |.-... Ot ete ae Dad ee eee dOSis5-5 os... 2 97 | Used garden hose,
small tree.

Dec. 3,1918 | Distillate emulsion....} 1 to5............- 3 60 | Hibernating larve.

Mar. 5,1919 | Crude-oilemulsion..__|_.... GOs eee Mees 3 60 Do.

ae a dose |sDistillateemulsions. -|1to4...) 2 S23 8 60 Do.

TIE do-=--~-+| Kerosene emulsion. -.-|1t04.5...-...:.2.- 3 25 Do.

pe at Gone el Distillateemulsion= =.) lto4— 22)... .: 1 65 Do.

pret 1919 |=. : GO Gakic bea Stee ees es UC a eee 3 60 | Trees in leaf, slight

burning.

Jan. 19,1920 | Crude-oilemulsion....| 1 to5......-...... 4 60 | Hibernating larve.

fhe does sees Distillate enrulsion. | 1 to 4 2.2. 3.22... 3 20 Do.

NST SGis 5 ye SE SENG Ks se es eee cere I rok pe ce 3 20 Do.

Apr. 12,1919 | Fish-oilsoap.......... 1 pound to 7 gal- 3 5 | Trees in leaf, no burn-
lons. ing, young females.

yess dope es Etinie-sulp huts a 1 GOO seo a 3 20 Do.

Dec. 3,1918 | Miscible oil, 33°...__.. etoulo see ee 5 10 | Hibernating larve.

Mar. 5,1919 Miscible oil, Aare ieee GOT see te 3 99 Do.

Jan. 19,1920 |..... iis, 2. a eee fea Meee dosceperien 4 98 Do.

eee Beene elo, ge wm | AGG... ee 2 100 Do.

Mar. 4, 1920 ove 5 ee Se eee dsc 522 ate 4 30 Do.

Suse ene ere O Ste en IEG 1D a 3 20 Do.

ae: pose” MMiscibie oil, DB gat SARE OO. eae oe. = b= 3 97 Do.

Dense ae |e aes OL os oe ek A OMe see eee 4 99 Do.

Apr. 18, 1920) |. 222 COPE ets Paes WE Osh Re ee a= ee 2 40 | Young females.

= oe 60 Oa ee od ees CG ae pe es ore Ocean sero: 2 95 Do.

Sn Ee aes te “a 1A SIO gpa rae rire (BS US 0 al yee a a 1 8 Do.

In experiment No. | the trees were large, in No. 3 the tree was
medium-sized, and in all the others the trees were snail and could
be sprayed from the ground with an ordinary bucket pump. This
was the apparatus used, except in the first four experiments, where
water was applied. All but one of the experiments were performed
at San Jose, Calif., upon the elms growing on the normal school
grounds.

WASHING EXPERIMENTS.

Washing the scale from the elm trees with a solid stream of water
was experimented with, since fairly good results had been obtained
in this manner by Prof. S. B. Doten, of Nevada (3, 4). In fact, his
results seemed more satisfactory than spraying onale a lime-sulphur
solution or kerosene emulsion.

In preliminary experiments, it was found ‘that the best nozzle
that could be obtained for the usual pressure of 50 pounds to the
square inch on the garden hose was one with a 3/16-inch outlet and
a long taper,

14 BULLETIN 1223, U. S. DEPARTMENT OF AGRICULTURE.

On small trees this equipment was used to good advantage to wash
the mature scale insects from their resting places. (Fig. 4.) All
limbs were within easy reach and the trees so small that a thorough
washing was possible. The results obtained were highly satisfac-
tory and the trees remained clean until reinfested in the fall.

On medium-sized trees the same apparatus was used, with the ad-
dition of a 12-foot platform and a 7 or 8 foot extension rod. This
proved to be too te-
cious and was only
moderately success-
ful even when done-
carefully.

On large trees it

yas necessary tog
have a greater pres- ©
sure and volume of
water in order to
obtain satisfactory
results. This was
obtained by using a
fire engine, supple-
mented with 1,000
feet of 23-inch hose,
a short tapering noz-
zle with a circular
g-inch opening, and—
a stand to facilitate
holding the nozzle.
(Fig. 5.)

It was possible to
use a pressure of
160 pounds without
doing any damage
to the foliage al-
ready out. It proved
beneficial, in fact, by
removing all dead
twigs and branches
and incidentally giv-
Fre. 4.—Washing young elm tree with garden hose and ing the trees and

nozzle to remove the European elm scale. lawns a good ITTrl-
gating.

The crew consisted of one foreman, one engineer, and three hose-
men, this number being necessary in order to move the heavy hose
without delay. te

With this apparatus and crew 191 large trees were satisfactorily
washed in six days at an approximate cost of $1.20 per tree. Dur-
ing al] the following summer the trees remained very clean, one or
two showing evidence of the presence of a few scale insects by a
shght drip. The writer estimated that about 85 per cent of the
scales had been removed. One year later, however, the trees were
again infested rather badly, owing partly to the remaining 15 per
cent and to a reinfestation from the surrounding well-infested trees.

P
’
;
,

=

THE EUROPEAN ELM SCALE IN THE WEST. 15

The results of these washing experiments have been previously re-—
ported in considerable detail (7).

SPRAYING EXPERIMENTS.

Sprays consisting of distillate emulsion, kerosene emulsion, or
erude-oil emulsion at strengths varying eae. 3 to 5 parts water to
1 part emulsion proved entirely unsatisfactory for the control of the
European elm scale, only 20 to 60 per cent of them being killed. A
solution of 1 pound of fish-oi] soap and 7 gallons of w ater was used
upon some molting females but was completely unsuccessful. <Al-
though other experimenters have reported fair results from the use
of lime- sulphur, the writer’s results with it were unsatisfactory,
practically none of the insects being killed. This material can not
be used in shade-tree work to any oreat extent because the sulphur
in it combines with the paint on buildings and turns it black.

Fic. 5.—Washing large elm trees with water from fire engine to remove the European
elm scale.

The best results were obtained from miscible-oil sprays. Those
containing 28° Baumé oil were found to be very satisfactory, whereas
those containing 33° gave very poor results. The former were
efficient at the proportions of 1 part oil to 9 and 12 parts water, and
certain brands of them at the greater dilution of 1 to 15 parts water.
Miscible oil 28°, 1 part to 12 parts water, is the material to be re-
commended.

RECOMMENDATIONS FOR CONTROL.

Kither of two materials is recommended for the control of this
insect, a solid stream of water or a miscible oil spray. The garden
hose and nozzle may be used to good advantage where a few small

16 BULLETIN 1223, U. S. DEPARTMENT OF AGRICULTURE.

trees need to be rid of this pest. The ordinary pressure of water
from the hydrant will remove the insects at a distance of 10 or 12 _
feet. Each limb and twig must be hit with a solid stream of water
from at least two directions. The use of a fire engine and equipment
is quite satisfactory on trees over 20 feet high. It probably does not
produce as good results as when a high-capacity spray, outfit is used,
but when the former is available and the latter is not, it is recom-
mended for large trees. It is cheaper than spraying and can not
damage the elms.

All washing should be done in the spring just before the leaves
appear on the trees, usually about the middle of April. The fruits

Fic. 6.— Spraying large elms with high-power outfit to remove the European elm scale.

or small winged seeds begin falling from the trees about a week
before the leaves appear, thus providing a warning that the washing
should be done soon. At this time the female scales are large, being
full of eggs, and are easily washed from the trees. This washing
could be done at any time until egg laying begins, five or six weeks
later, were it not for the presence of the foliage, which impedes the
force of the stream. Thus to insure success in washing there must be
a solid, forceful stream of water, and it must be used at the proper
time.

THE EUROPEAN ELM SCALE IN THE WEST. tt

A more satisfactory method of control is the use of miscible oil
containing 23° to 28° Baumé oil, which can be obtained from dealers
under various trade names. This should be used in the following
proportions:

Miscible oil (23° to 28° Baumé) ____ ____ 1 gallon or 16 gallons.
AO NTE lla SR age i ae Se 12 gallons or 184 gallons.

It is mixed by first pouring the requisite amount of oil into the
spray bucket, barrel, or tank to be used and then adding a small
amount of water. With considerable agitation this will become light-
colored and of a creamy consistency, whereupon more water may be
added, and finally all the water, in the meantime agitating thor-
oughly. This may then be applied with any sort of spray outfit,
providing the apparatus has power enough to send a spray to the
tree tops.

The bucket or barrel pump will do very well for small trees, the
ordinary orchard power outfit for trees up to 40 feet in height, and a
high-power apparatus for trees above this height. (Fig. 6.) <A
pump registering a pressure of at least 800 pounds with a capacity
of 12 to 15 gallons or more per minute is necessary to reach trees 60
to 90 feet high, which is often the height of mature elms. A spray
gun or solid-stream Worthley nozzle is necessary to force the spray
to the tops of the trees from the ground. The use of a smaller outfit
and ladders is not to be recommended, on account of extra cost and
unsatisfactory results.

Large trees require from 30 to 50 gallons of mixture, costing from
3 to 4 cents per diluted gallon for the material and 14 to 24 cents per
gallon to apply it.

Every branch and twig should be covered, but too much spray
should not be allowed to settle about the base of the tree, as it might
injure the roots. No damage to elm trees or lawns has been noted,
however.

The spraying should be done in the winter up to the time the
buds begin to open in the spring. Probably a weaker spray could
be used on the young forms in the late summer but this would be
about as expensive, for nearly twice the amount of material would
be required to cover each tree on account of the foliage, and it
would be much less satisfactory since all parts, particularly the
underside of the leaves, which are the most heavily infested, could
not be thoroughly covered.

If properly done, spraying should not be necessary every year,
except upon young trees, which seem to become reinfested easily
when near unsprayed large trees. Extermination, of course, is not
to be hoped for, but it is possible to kill a sufficiently high percent-
age of the insects to prevent their appearance in large numbers the
following season.

SUMMARY.

The European elm scale was introduced into this country about
1884 from Europe and was first found at Rye, N. Y. From there
it has spread until it is now located in 27 States and the District of
Columbia. Although more widespread in the East, the injury to

69577 °—24——_2

18 BULLETIN 1223, U. S. DEPARTMENT OF AGRICULTURE.

trees is not as great as in the West. This insect infests only elms,
doing damage particularly to young trees, but killing twigs and
branches of the older ones. It causes the leaves to turn yellow and
drop early, besides making foliage and ground black and sticky
from its secretion of honeydew.

The first-stage larva is a small, yellowish, oval object about 0.5
millimeters long. The second-stage larva is over twice as long
as the first, and is reddish brown, but appearing gray from the
waxy coat on its back. The adult female is large and oval, about
2 millimeters long, and of a dull red-brown or green-brown color,
surrounded by a white cottony fringe of wax.

The second-stage larvee hibernate in the bark crevices and about.
the winter buds. In early spring the male larve form cocoons
and transform in them to adults. By this time the female larve
have molted and seek a sheltered place on the underside of the limbs
and branches. After mating they form a waxy fringe about their
bodies and in late spring or early summer begin to deposit their
egos. This they continue to do throughout the summer, and upon
completing oviposition they shrivel and die. The larve hatch very
soon from these eggs and crawl to the midribs of the leaves or in
some case remain in the bark crevices. All molt to the second stage.
Those on the leaves move in the fall to more premanent winter
quarters on the twigs and about the buds, where they remain until
activity begins again in the early spring.

Several lady-beetles feed upon the European elm scale but are
not plentiful enough to be considered as important enemies. A num-
ber of sprays have been experimented with, but only washing in
the spring with a solid stream of water and spraying in the winter
with a solution of 23° to 28° Baumé miscible oil, 1 part oil to 12 parts
water, have proved effective in the control of this pest.

LITERATURE CITED.

(dl) CooLEy, Roa:
1898. Notes on some Massachusetts Coccidae. In U. 8. Dept. Agr., Div.
Ent.. Bul. 17,/n. 's., p. 61-65.
(2) CrRAw, ALEXANDER.
1894. Entomology and quarantine. Jn 4th Bienn. Rept. Sta. Bd. Hort.
Calif., 1893-1894, p. 79-109, pl. 37-88, figs.
(3) Dotren, SAMUEL B.
1908. The European elm scale. Nevada Agr. Exp. Sta. Bul. 65. 34 p.,

14 pil.
CN eae
1910. Spraying trees for the elm scale. Nevada Agr. Exp. Sta. Cire. 6.
6 p., 3 fig.
(5)

1912. The European elm scale. Jn Mo. Bul. Calif. Sta. Comm. Hort.,
v. 1, no. 3, p. 89-100, fig. 28-37.
(6) Essic, E. O.
1915. Injurious and beneficial insects of California. Suppl. Mo. Bul.
Calif. Sta. Hort. Comm. 541 .(-+lxxxi) p., 503 fig. :
(7) FELT, EPHRAIM PORTER.
1905. Elm bark louse. N. Y. State Mus. Mem. 8, p. 203-207. Bibliog-
rapiy. Wa 20K.
(8) HartTzeELit, ALBERT.
1921. Distribution of the European elm scale. Jn Proce. Iowa Acad.
Sci. for 1921, v. 28, p. 201-205, fig. 31.

(9)
(10)
(11)
(12)
(13)

(14)
(15)

(16)

(17)

(18)

(19)

(20)

THE EUROPEAN ELM SCALE IN THE WEST. 19

HERBERT, F. B.
1920. Results of washing experiments for control of the European elm
scale. Jn Journ. Econ. Ent., v. 13, no. 6, p. 471-475.
Howakrp, L. O.
1889. A newly-imported elm insect. In U. S. Dept. Agr., Div. Ent.,
Insect Life, v. 2, p. 3441, fig. 1-5.
Kuwana, S. I.
1907. Notes on the life history and morphology of Gossyparia ulmi
Geoff. Jn Bul. Imp. Centr. Agr. Exp. Sta., v. 1, no. 2, p. 213—
231, pl. 35-36. Tokyo, Japan.
LINDINGER, LEONHARD.
1912. Die Schildliuse (Coccidae). 388 p., 36 fig. Stuttgart.
LINNAEUS, CAROLUS.
1758. Systema naturae. 10th ed. rev., t. 1, 824 p. Holmiae.

1761. Fauna Svecica. 578 p. Stockholm.
List, GEORGE M.
1920. The European elm scale. Office State Ent., Colorado Agr. Coll.
Cire. 23. 12 p:, A pl.
MELANDER, A. L.
1906. Two insect pests of the elm. Wash. Agr. Exp. Sta. Bul. 74. 7 p.,.
1 fig.
MopEER, ADOLPH.
1778. Om Fastiflyet (Coccus). Goetheborgsk, Vetensk. -Handl. Stiiek
1, no. 1, p. 11-50. Not seen.
REAUMUR, M. DE.
1738. Des progallinsectes de la cochenille, et de la graine d’Ecarlate de
Pologne. Jn Mémoires pour servir a l'histoire des insectes, t. 4,
Mém. 2, p. 81-122, pl. 7.
SIGNORET, V.
1875. Essai sur les cochenilles ou gallinsectes. (Séance du 11 novem-
bre 1874.) Jn Ann. Soc. Ent. de France, 5e sér., t. 5, p. 15-39.
WALLACE, FRANK N.
1915-1916. Ninth annual report of the State Entomologist of Indiana.
230 p., 60 fig.

ORGANIZATION OF THE
UNITED STATES DEPARTMENT OF AGRICULTURE.

October 24, 1923.

meer etarg oF Agriciiture:- >. = = ss eo oe HENRY C. WALLACE.
Assistant. Secrevary No Sa. Se Howarp M. Gore,

TPC CLOT-OF SCICTLANG WOnl 222 Wee BD. Bar,

Director of Regulatory Work _~__- 2 -~ W ALTER G. CAMPBELL.

Director of Hzxtension Work______- Ps Pe SO C. W. WARBURTON.

pre CET 00 = one ap Os 2 ie a ee R. W. WILLIAMS.

NEDTA CLAS EXD 211 |) Se a ep APM ee EE CHARLES F. MArvIN, Chief.
Bureau of Agricultural Heonomics___________- HENRY C. TAYtor, Chief.
Bureau of Animal Industry___ 2s JOHN R. MouHTLER, Chief.
iGareawo; Plant nausi yg ee ae eee WILLIAM A. TAYLOR, Chief.
PIGMENT ES EIUICE.. 2-3 a5: + an Cee e 18 7 EE ee ee! W. B. GREELEY, Chief.

Bareau of Chemistry 2 ae ree ee te C. A. BRowNng, Chief.
WSUTEDUAO/. SOUS Soe Se ont AWS Sal er MILTON WHITNEY, Chief.
Perea Of Entomol gus2 = a se es L. O. Howarp, Chief.

Bureau of Biological Survey____. 2 EK. W. NELSON, Chief.

BUTetu OF PUbUG ROGdS. =k. 2 3.) a ee = THOMAS H. MACDONALD, Chief.
Bureau of Home Hconomics.__-—___-—_-__-____- LOUISE STANLEY, Chief.

Office of Experiment Stations_________ ______ EK. W. ALLEN, Chief.

Fixed Nitrogen Research Laboratory________ F. G. CoTTretyt, Director.
CATT CHIROILS © =< om eee tS 78 Sg ee oe L. J. HAYNES, in Charge.
JOLT, x | ea NE ee ee, eee eA CLARIBEL R. BARNETT, Librarian.
Meceral Horlicitihirel Board _. ao C. L. MARLATT, Chairman.
Insecticide and Fungicide Board_____________ J. K. HAYwoop, Chairman.
Packers and Stockyards Administration______. CHESTER MorrRIL, Assistant to the
Grain Futures Administration________-____. Secretary.

This bulletin is a contribution from

Bureaworpatomowgy. > ee L. O. Howarp, Chief.
Forest Insect Investigations________.____. F. C. CRAIGHEAD, Entomologist in
Charge.
20

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